OBJECTIVES: 1. Determine the effect of prostaglandin on salt transport across the thick ascending limb of Henle and distal convoluted tubule. 2. Examine the effect of aldosterone on bidirectional sodium fluxes across the collecting duct. 3. Examine the nature of H secretion/HCO3 reabsorption across the proximal and distal tubules. 4. Delineate the factors responsible in the development of two types of proximal nephrons.